An aromatic carbonate is an eco-friendly carbonyl source capable of replacing phosgene, which is a very toxic compound. An aromatic carbonate can be obtained through reaction of an aromatic alcohol compound with carbon monoxide, carbon dioxide, urea, and the like. However, this method has problems of generation of by-products during reaction, inclusion of impurities in a product, use of an expensive catalyst, complex processes, and the like.
To overcome these problems, a method for preparing an aromatic carbonate through transesterification between an aliphatic carbonate and an aromatic alcohol has been developed. Here, compounds such as PbO, TiX4 (X=an alkoxy group, an aryloxy group, or a halogen group), and SnR2(X)2 (R=an alkyl group, an alkoxy group, an aryloxy group, or a halogen group) are considered to be a desirable catalyst. Since these catalysts generate water, an alcohol, a halogen compound, and the like through reaction with an aromatic alcohol, these catalysts are converted into a metal phenoxide through pretreatment with an aromatic alcohol in preparation of an aromatic carbonate, instead of being directly used. However, this method has problems of difficulty of transportation due to low solubility of a metal phenoxide, cumbersome pretreatment, and catalyst preparation costs.
There has also been developed a method wherein carbon dioxide is reacted with ethylene oxide and the like to prepare a cyclic carbonate, followed by reacting the carbonate with an aliphatic alcohol, thereby producing an aliphatic carbonate to be used in preparation of an aromatic carbonate. This method has advantages in that harmless carbon dioxide is used as a carbonyl source, and corrosive materials such as hydrochloric acid are hardly used or generated. However, this method can cause side reactions such as generation of ethylene glycol, and has a limitation relating to plant location due to difficulty in safe transport of ethylene oxide or ethylene, which is a source of ethylene oxide.
Recently, a method for preparing an aliphatic carbonate by reacting carbon dioxide, as a carbonyl source, with an organometallic compound has been studied. It has also been found that, after separation of an aliphatic carbonate from a mixture produced by the method, the organometallic compound can be reproduced by reaction of a residual liquid with an alcohol. In other words, the used organometallic compound can be recycled to be reused in formation of the aliphatic carbonate. As such an organometallic compound, there are disclosed compounds of formula Sn(R)2(OR′)2 (R and R′ being two different alkyl groups), which includes tin as a center metal and contains two alkyl groups and an alkoxy group (Japanese Patent Application No. 2010-523783 A, No. 2006-548937 A, No. 2006-513613 A, No. 2006-095140 A, No. 2005-511122 A, No. 2003-556375 A, No. 2001-396545 A, No. 2001-396537 A, and the like).
However, these organometallic compounds must be regenerated after reaction in order to be recycled. Therefore, there is a need for a method which can avoid costs for regeneration of an organometallic compound and can economically prepare an aromatic carbonate in high yield using carbon dioxide as a carbonyl source without a need for use of an expensive catalyst, complex processes, and the like.